Hi Doc. Universe, I was wondering how vaccines work because I would really like to make a better way to get a shot that doesn't hurt so much. Thanks. -Jacob, 10, Cayman Islands

The quick, little sting of a vaccine shot can provide us with some big protection from germs that cause disease.

One kind of germ is a virus. Viruses are so small that you can’t see them even with a normal microscope. But if you use a more powerful electron microscope, you’d see each one wears a kind of coat with bits and knobs that stick out in different directions.

“Just like every person’s face looks different, every virus coat looks different,” said my friend Felix Lankester, a veterinarian at Washington State University.

He knows a lot about viruses, especially one that causes a serious disease called rabies. His team helps set up clinics in Africa to deliver life-saving rabies vaccines to animals. He offered to help us investigate how vaccines work.

Vaccines help kick your body’s big defense network, or immune system, into gear. When you get a flu vaccine, for example, you get a little bit of the flu virus. The virus doesn’t hurt you, though.

It’s in a really weak form but your white blood cells still notice something unusual is going on. They react by making Y-shaped parts called antibodies that attach to the virus’s coat.

“The bits that stick out of the coat of the virus are what antibodies recognize,” Lankester said. “It stimulates an immune response.”

The antibodies attack and tag the invading germs so your body knows to recognize and destroy them.

Your immune system doesn’t just fight off the germ, though. It actually memorizes it.

Particular kinds of cells in your body remember the different viruses that enter your system. It helps you build up what we call immunity. That way, if the virus returns, your body knows how to respond. It can fight off the invader before it makes you sick.

Memory cells are part of the reason we only get sick from some viruses once. When you get the chicken pox virus, your cells are able to remember. Then, if you get exposed to chicken pox virus again, your body knows to get rid of it quick and how.

Vaccines have helped eliminate serious diseases like smallpox and polio in many parts of the world. Rabies is a horrible disease that still affects people and our fellow animal friends. There is a vaccine for it, but some people live too far from hospitals and veterinary clinics to get it.

So delivering rabies vaccines to people who need it is really important. Lankester and friends at WSU are working toward a vision of a world without rabies, saving the lives of both people and their pets.